Furnace operation with regenerators, or with thermochemical regenerators (TCR), is an efficient heat recovery system for high temperature industrial furnaces such as glass melting, steel heating and aluminum melting, especially when operated with oxy-fuel fired burners. Regenerators provide a way to capture the heat contained in the gaseous combustion products (flue gas), and to use the captured heat to preheat oxidant or fuel that is fed to the furnace. A more efficient system is to employ regenerators to preheat both the fuel and the gaseous oxidant (which could be air, or a stream whose oxygen content is up to 100 vol. % oxygen), so that the heat recovery efficiency is improved and the flue gas exiting the regenerator is cooled below 1000 F.
Regenerator chambers are often separated by a single shared wall. For example the conventional air heating regenerator for an end-port glass melting furnace has two chambers, an air preheating chamber and a flue gas heat recovery chamber, which are directly adjacent to each other and separated by a single shared wall made of refractory material. As the regenerators age, often cracks are developed in refractory walls, including the shared wall, and the gas in the chamber with a higher pressure can leak into the adjacent chamber through the shared wall. For the case of air heating regenerators gas leakage through the shared wall causes a small loss of the combustion air into the flue gas stream. While the leak of combustion air reduces the efficiency of the heat recovery process, it does not cause safety or emissions issues. For TCR and O2 heating regenerators gas leaks through shared walls not only cause loss of fuel or oxygen into the flue gas stream with potential emissions issues, but also could cause mixing and combustion of fuel and oxygen in the regenerators. The potential problems of gas leaks through refractory walls also apply to the external walls for TCR and O2 heating regenerators. Gas leaks through external walls cause loss of fuel or oxygen to the ambient in the upper section of the regenerator chamber where the gas pressure inside the regenerator chamber is higher than the ambient pressure or ambient air leaks into the regenerator chambers in the lower section of the regenerator where the regenerator gas pressure is lower than the ambient pressure. Although external wall gas leaks can be controlled by installing external gas tight metal shells, there is potential for gas leaks from imperfect joints and seals.
The present invention provides improved heat recovery efficiency in furnace operations that employ regeneration or thermochemical regeneration with the fuel and the gaseous oxidant.